A number of applications of integrated electronic circuits may benefit from an additive manufacturing process, such as printing. Manufacturing processes that avoid subtractive processes such as photolithographic patterning and etching may enable integrated circuitry to be formed on rigid or flexible substrates. Particularly attractive applications for such manufacturing technology include flexible display devices and identification tags (e.g., RFID tags).
Low cost RFID systems, typically including an interrogator or “reader” and an electronic label or “tag,” are desirable in a variety of applications, such as retail, supply chain management, logistics, library management, and baggage claim systems, as just a few examples. Other emerging applications include vehicle toll tracking and/or management. One advantage of RFID systems over conventional barcode and magnetic media-based systems is that RFID systems can be configured to read multiple electronic labels simultaneously.
Referring now to FIG. 1, a block diagram showing a conventional RFID tag system for a single tag application is indicated by the general reference character 100. Computer 102 can connect (wirelessly or through a wired connection) to interrogation source or reader 104, which can then communicate to tag 110 via antenna 106. Tag 110 can provide information wirelessly to antenna 106 that can then be captured by detector 108 and fed back into computer 102. Tag 110 can, for example, provide a simple bit string of data back to computer 102. For example, in a retail application, tag 110 can convey to computer 102 information regarding the item to which it is attached. The information may include various attributes or properties of the item, or whether the particular item has been purchased or not.
Referring now to FIG. 2, a diagram showing a conventional UHF tag system application for reading multiple tags simultaneously is indicated by the general reference character 200. For example, toll station 206 can employ a tag system to determine whether cars passing through have arranged for payment (e.g., via a debit or a credit account) to access a road, as an alternative to each car stopping in order to pay a person in a booth at the toll station. Each car passing through may have an associated tag attached to the vehicle (e.g., tags 202-0, 202-1, and 202-2). An applied electromagnetic field can include UHF waves 208 that pass information between interrogator/reader 204 and each of tags 202-0, 202-1, and 202-2. Other such multi-tag read applications include HF, VHF and RF circuitry in the retail, library or inventory management, security, and animal (e.g., pet) identification fields, for example.
Thin film transistors (TFTs) may be used in various implementations of printed devices. In theory, TFTs can be used in forming a frequency divider for on-chip clock generation and other logic control. However, TFTs generally exhibit relatively high leakage current and relatively low switching speed, as compared to metal oxide semiconductor field effect transistors (MOSFETs) made from monocrystalline and polycrystalline silicon (e.g., monolithic circuits and/or devices).